Azo-dyestuffs



United States AZO-DYESTUFFS Max Schmid and Willy Mueller, Riehen, Switzerland, assignors to Ciba Limited, Basel, Switzerland, a Swiss firm No Drawing. Application May 8, 1958 Serial No. 733,851

Claims priority, application Switzerland May 17, 1957 8 Claims. (Cl. 260-176) The present invention provides new azo-dyestuffs which correspond to the general formula which is free from groups imparting solubility in water,

in which formula A represents the radical of a coupling component containing two enolizable keto-methylene groups, and each symbol B represents an aryl radical.

The dicarboxylic acids of the Formula 1, of which the dihalides are used as starting materials in the process of this invention, may contain as the radical A a dipyrazolone radical, for example, a radical of the formula Of special interest are those dicarboxylic acids which correspond to the formula OOH OOH in which R and B represent aryl radicals. B is advantageously a benzene radical, and R is, for example, a

2,936,306 ?atented May 10, 1960 diphenyl radical and advantageously a benzene radical bound to the -NH groups in the 1:4-positions, and which contains in the nucleus at least one suhstituent, for example, a halogen atom or an alkyl or alkoxy group.

The aforesaid dicarboxylic acids are advantageously prepared by coupling-two molecular proportions of diazotized monoamine-monocarboxylic acid which is free from groups imparting solubility in water and is advantageously of the aromatic series, with one molecular proportion of a coupling component which is free from groups imparting solubility in water and contains two enolizable keto-methylene groups, advantageously a compound of the formula which can be obtained in a simple manner by the reaction of diketene or acetoacetic acid ester with an aromatic diamine. As examples of suitable coupling components there may be mentioned the bis-acetoacetyl-compounds of the following diamines:

1 :4-diaminobenzene,

l B-diaminobenzene, 1 :3-diamino-4-methylbenzene,

1 3-cliamino-4-methoxybenzene, 1 3-diamino-4-chlorobenzene,

1 :4-diamino-Z-chlorobenzene, l :4-diamino-2-bromobenzene,

:4-diamino-2 S-dichlorobenzene, z4-dian1ino-2-methylbenzene,

: 4-diamino-2 5 -dimethylbenzene, :4-diamino-2-methoxybenzene,

:4-diamino-2: S-tlimethoxybenzene, :4-diamino-2:S-diethoxybenzene,

:3-diamino-4 G-dimethylbenzene,

:3-diamino-2 2 6-dimethylbenzeue,

:4'-diamino-diphenyl,

: 3 '-dichloro-4 4-diaminodiphenyl,

: 3 '-dimethyl-4 4'-diaminodiphenyl,

: 3 '-dirnethoxy-4 4-diaminodiphenyl,

:3 '15 5 -tetrachloro-4 4'-diaminodiphenyl,

: 3 -dichloro-5 5-dimethyl-4 4-diaminodiphenyl,

: 4' diarnino-diphenylmethane,

:4-dimethoXy-3 3 '-diamino-diphenylmethane, 424'-diamino-diphenylamine,

4:4-diamino-diphenyl oxide,

4:4-diamino-diphenyl ketone,

2: S-diaminochrysene,

4: ll-diamino-fluoranthene,

2:6- or 1:5-diaminonaphthalenes,

Diaminobenzthiazoles, such as 2-(4-aminophenyl) 6- aminobenzthiazole, and the amines of the formulae l l 1 1 l 1 l l 4 3 3 3 3 3 4 4 '1-aminobenzene-3-carboxylic acid, l-aminobenzene-4-carboxylic acid, l-amino-Z-methylbenzene-4-carboxylic acid, l-amino-Z-chlorobenzene-4-carboxylic acid, l-amino-Z-chlorobenzene-S-carboxylic acid, 1-amino-4-chlorobenzene-S-carboxylic acid, l-amino-Z-methoxybenzene-S-carboxylic acid, 1-amino-Z-chloro-5-methoxybenzene-4-carboxylic acid, 1-amino-2:4-dichlorobenzene-S-carboxylic acid, 1-amino-2-nitrobenzene-S-carboxylic acid, 4'-arnino-diphenyl-4-carboxylic acid.

The azo-dicarboxylic acids of the Formula 1 are treated with an' agent capable of converting carboxylic acids into halides thereof, for example, their bromides or chlorides. As examples of such agents there may be mentioned phosphorus halides, for example, phosphorus trichloride, phosphorus pentachloride and phosphorus oxychloride, and more especially thionyl chloride. The treatment with such acid-halogenating agents is advantageously carried out in an'inert organic solvent, such as a chlorobenzene, for example, monoor di-chlorobenzene, toluene, xylene, benzene or nitrobenzene. When thionyl chloride is used as acid-chlorinating agent it is of advantage to work in the presence of a dialkylformamide, more especially dimethyl formamide.

In preparing the carboxylic acid dihalides it is generally of advantage first to dry the azo-compounds that have been prepared in an aqueous medium, or to remove the water therefrom by boiling them in an organic solvent accompanied by azeotropic distillation. This azeotropic drying, may, if desired, be carried out immediately before the treatment with the acid-halogenating agent.

In the process of this invention the dicarboxylic acid halides so obtained are reacted with primary amines, advantageously those of the aromatic series. As suitable amines there may be mentioned principally those of the benzene series, for example, unsubstituted aniline, nuclear halogenated anilines, for example, ortho-, paraor metachloraniline, 2:5-dichloraniline, 3:425 trichloraniline, para-bromaniline, nitranilines such as ortho-, paraor meta-nitraniline, alky-anilines, for example, orthoor paramethoxyaniline, nuclear alkylated anilines such as nuclear alkylated toluidines or meta-'xylidines, or halogenalkyl anilines such as3-trifluoromethyl-aniline or 3:5- di-(trifiuoromethyl)-aniline, or phenyl-aniline's such as para-aminodiphenyl, or aniline containing functionally converted carboxy groups, for example, carboxylic acid ester groups, cyano groups or carboxylic acid phenyl amide groups. Among these latter compounds there may be mentioned the following:

Aniline-Z-carboxylic acid ethyl ester, Aniline-3-carboxylic acid methyl ester, Aniline-3 :S-dicarboxylic acid dirnethyl ester, 3-cyano-aniline, 7 I 3- or 4-ani1ine carboxylic acid anilide.

There may also be used anilines containing various substituents, for example,

2-chloro-5-methylaniline, 4-chloro-2-methylani1ine,

. 4 Z-methyI-S-chIoraniline, 2-chloro-4-nitroaniline, 2-chloro-S-trifluoromethylaniline, 4-chloro-2-trifluoromethylaniline, 2-nitro-4-chloraniline, 4-chloro-2-methoxyaniline, 2-chloro-4-niethoxyaniline, 4-chloro-2-methoxy-S-methylaniline, 2-nitro-4-methylaniline,

4- or S-nitro-Z-rnethylaniline ;-nitro 2-methoxyaniline,

4-chloro-2 S-dimethoxyaniline.

There may also be used polynuclear aromatic amines, for example, aminonapthalenes, aminoanthraquinone or aminopyrene.

The condensation of the carboxylic acid halides of the kind defined above with the amines is advantageously carried out in an anhydrous medium. .Under these conditions the condensation usually takes place surprisingly easily even at temperatures Within the boiling range of normal organic solvents, such as toluene, monochlorobenzene, dichlorobenzene, trichlorobenzene, nitrobenzene and the like. In order to accelerate the reaction it is generally of advantage to use an acid-binding agent, such as anhydrous sodium acetate or pyridine. Some of the dyestuffs so obtained are crystalline and others are-amorphous, andthey are generally obtained in very good yield and in pure state. It is of advantage first to separate the acid chlorides obtained from the carboxylic acids. In some cases separation of the acid chlorides may be dispensed with without harm, so that the condensation is then carried out directly following the preparation of the carboxylic acid chlorides.

The dyestuffs of this invention are valuable pigments which, owing to their insolubility in organic solvents and their heat resistance, are excellently suited for dyeing plastic materials, especially polyvinyl compounds, tints which range from greenish yellow to orange. Of special interest are the dyestufis of the general formula in which R, and B represent aryl radicals. These dyestuffs are distinguished by their especially good fastness 7 7 paper, for example, wallpaper or fabrics of glass fibers,

by means of a suitable adhesive, such as casein, a hardenable synthetic resin, especially a urea-formaldehyde or melamine-formaldehyde condensation product, polyvinyl chloride or polyvinyl acetate solutions or emulsions or other emulsions (for example, oil-in-water or water-in-oil emulsions).

The pigments of this invention can also be used, for example, in finely dispersed form fordyeing artificial silk from viscose or cellulose others or esters or superpolyamides or superpolyurethanes in the spinning mass, and also for the preparation of colored lacquers or lacquer formers, solutions and products of acetyl-cellulose, nitrocellulose, natural resins or synthetic resins, such as polymerization or condensation resins, for example, aminoplasts, phenoplasts, polystyrene, polyethylene, polyacrylates, rubber, casein, silicone or silicon resins. They are also of advantage for the manufacture of colored pencils, cosmetic preparations or laminated sheets. e

with ortho-dichlorobenzene until colorless. The crystalline mass is then washed with Preparations which contain such pigments in finely dispersed form, can be obtained in known manner by intense mechanical treatment, for example, on a roller mill or in a suitable kneading apparatus. The dispersion medium in which the intense mechanical treatment is carried out, is chosen depending on the manner in which the preparation is to be used, for example, for the production of preparations that are dispersible in water there may be used sulfitc cellulose waste liquor, or a salt of dinaphthylmethane disulfonic acid may be used for the production of cellulose acetate artificial silk spinning compositions by mixing the salt in a small amount of solvent with acetyl cellulose.

Owing to the especially favorable physical form in which the products of the invention are usually obtained, and owing to their chemical inertness and good heat resistance, they can generally be dispersed easily in compositions or preparations of the above kind, and this isadvantageously carried out at a stage at which the composition or preparation has not reached its final form. The necessary operations for shaping, such as spinning, ressuremoulding, hardening, casting, sticking or the like, can also eno drying the product in vacuo at 5060 C., thereare obtained 65 parts of the dyestufi acid chloride as an orange crystalline powder. It is very sparingly soluble in organic solvents. It can be recrystallized from hot nitrobenzene in small amounts. At temperatures above 280 C. it decomposes without melting.

14.l2 parts of the acid chloride so obtained are heated in 200 parts of ortho-dichlorobenzene with 0.1 part of thionyl chloride up to 106 C. A solution of 3.8 parts of aniline and 2 parts of pyridine in 20 parts of dichiorobenzehe is then added and the whole is stirred for 12 hours at 135440 C. The pigment so formed is filtered ofi with suction while hot and washed with hot ortho-dichlorobenzene until the washings are completely colorless. The ortho-dichlorobenzene is then displaced by methanol, and the product is finally washed with hot water. By drying the product there is obtained a loose soft pigment, which is practically insoluble in the usual solvents, and when rolled into polyvinyl chloride yields bright rich reddish yellow tints of very good. fastness to migration and light. The pigment so obtained corresponds to the formula The following examples illustrate the invention, the

parts and percentages being by weight:

Example 1 66.9 parts of the dyestuff obtained from 2 mols of diazotized 4-chloro-3-aminobenzoic acid and 1 11101 of 2:5- bis-acetoacetylamino-l:4-dimethylbenzene of the formula COOH are stirred in 600 parts of ortho-dichlorobenzene with 5 parts ofdimethylformami'de and heated to95l00 C.

At that temperature 32.8 parts of thionyl chloride are run in in the course of 15 minutes, and the whole is then stirred for a further 2 hours at 100-1l0 C. The reaction mixture is in this manner converted into a thick crystalline magma. The end of the reaction can be recognized by the cessation of the evolution of hydrogen chloride, and by the fact that a test sample examined under the microscope consists of unitary reddish yellow needles. The mixture is then allowed to cool to 80 C. and filtered with suction. The filter residue is washed the filtrate is almost benzene and towards the end with petroleum ether. After 33.45 parts of the dry dyestuft obtained from 2 mols of diazotized 4-chloro-3-aminobenzoic acid and 1 mol of 2:S-bis-acetoacetylamino-l:4-dimethylbenzene are stirred in 500' parts of orthodichlorobenzene with 2.5 parts of dimethylformamide and heated to 95 C. 16.4 parts of thionyl chloride are run in in the course of i0 minutes and then the whole is heated for 2 hours at ll5-l10 C. When the evolution of hydrogen chloride has subsided, a gentle current of air is sucited through the flask for 15 minutes in order to remove excess of thionyl chloride, hydrogen chloride and sulfur dioxide. 10.7 parts of ortho-toluidine and 5 parts or pyridine in 50 parts of ortho-dichlorobenzene are then rapidly added, and the reaction mixture is heated for 12 hours at 135-140" C. The whole is then allowed to cool to C., 5 parts of anhydrous sodium acetate are added, and the whole is stirred at that temperature for 15 minutes. The mixture is then filtered with suction, the filter residue is washed with hot ortho-dichlorohenzene until the washings are colorless. It is then washed with methanol, the washings being strongly colored at first. Towards the end the product is washed thoroughly with hot Water, and then dried at 100 C. in vacuo. There is obtained a loose soft yellow powder, which, when incorporated in plastic compositions, especially a polyvinyl chloride composition, yields reddish yellow tints which are fast to migration and very fast to light. By pigment printing there are obtained with this product prints that are fast to solvents.

In the following table are given further acid amide derivatives of azo-dyestutf dicarboxylic acids, which are obtained by coupling 2 mols of an aminoaryl-carboxylic acid mentioned in column I with 1 mol of the bis-acetoacetyl-aryl compound mentioned in column II. The azodyestutf dicarboxylic acids are converted with thionyl chloride into the dicarboxylic acid dichlorides and condensed with two mols of an arylamine mentioned in column I II III IV Tint of material Dials-component Coupling component Arylamine dyed with the dyestufl l 4-Chloro-3-am1no-benzoic acid..- 2:5-Bis-acetoacetyl-amino-1:4- o-Chloranillne pure yellow.

dimethyl-benzene.

4-Chloro-6-toluidine reddish yellow. 2-Methoxy-5methyl-eniline Do. 2-Methoxy-aniline greenish yellow. 3-Ghloro-2-methyl-aniline pure yellow.

5-Ohloro-Q-amino-toluene reddish yellow. 4-Methoxy-aniline. orange yellow.

'd' greenish yellow.

orange yellow. orange. d Do. 2:5-Bisacetoaeetylamlno reddish yellow.

methylbenzene. H n

.Zdo 2: 5-Dichloro-l: 4-bis-acetoacetylyellow-orange. reddish yellow. purebyellow.

o. greenish yellow.

' yellow-orange. smmobenzene. 19 do o-Toluidine reddish yellow. 20 4-Chloro-3-aminobenzoic acid.-. do Aniline veryngreenish ye ow. 21 do do o-Toluidine greenish yellow. 22 4-Ch1oro-3-aminobenzoic acid 2:5-Dichloro-1: bis-acetoaeetylo-Anisidine very greenish aminobenzene. yellow. 0 2:5-Diehloro-aniline greenish yellow. 2-Chloro-l:4-bis-ecetoacetyl- Aniline Do.

aminobenzene.

o-Toluidine pure yellow. o-Anisldine greenish yellow.

S-ChIoro-lmethoxy-anilme. Aniline pure yellow.

pure orange. aminobenzene.

o-Toluldine yellow orange. 5-Chloro-2-methoxy-aniline orangeyellow. 5-Methyl-4-Chloro-Z-methoxyorange.

aniline. do Aminopyrene reddish yellow.

2:5-Dimethoxy-1:4-bis-aeeto- Aniline scarlet red.

acetyl-arnino-benzene.

o-Toluldine.. scarlet. 4-Chloro-2anisidine o. 86- do Ohloro-cresidinered orange. 37 4-Methoxy-3-amiuobenzoic aci etyl-amino-1:3- Aniline greenish yellow.

zene.

Chloro-cresidine Do. o-Toluidinereddish yellow. Aniline... pure yellow. o-Anisidine greenish yellow. d 4-Chloro-2-an!sidine pure yellow. -Methoxy Aniline yellow.

acetyl-arninobenze do o-Toluidme. reddish yellow.

o-Anisidlne Do. 4-Chioro-2-anisidine. pure yellow.

yellow-orange. orange. greenish yellow.

5-Chloro-2-aminotoluene... Do. o-Toluidine Do. acetyl-aminobenzene. 2: 5-Dimethyl-3: 6-dichloro-1z4- o-Anlsidine.. Do.

bis-acetoaeetyl-arninobenzene. Z-Methoxy-1:4-bis-aeetoacety1- Z-Amlnopyrene yellow.

amino-benzene. 2:5-Dimethyl-1:4-bls-aceto- .T-Naphthylamlne reddish yellow.

acetyl-arnino benzene. 2: 5-D ichioro-l d-bis-acetoacetyl- 5-0hloro-i-amino-anthraquinone. yellow.

amino-benzene. 2: 5-Dimethyl-1 4-bis-acetoacetyll-Amino-S-benzoylamino-anthrabrownish yellow.

amino-benzene. (111' one. 57 B-Methyli-aminobenzoic acid--. 2:5-Dichloro-1:4-bis-acetoacetylniline reddish yellow.

amino-benzene. 58 4*Methoxy-3-a1nino-benzoie acid. 2:5-Dimethyl-l:4-bis-aceto- N-ethyl-anlline pure yellow.

aeetyl-amino-benzenc.

Example 3 robenzene is displaced with benzene and dried at 60-70 C. in vacuo. The chloride is obtained as a red-orange finely crystalline powder. It is extremely sparingly soluble in organic solvents, and it decomposes when heated above 290 C. without previously melting.

14.28 parts of the resulting acid chloride are stirred with 0.1 part of thionyl chloride in 200 parts of orthodiehlorobenzene and heated up to 100 C. There are ther 3 hours at 1104150 The end point of the then added 6 parts of ortho-phenetidine and' 2 parts of action is reached when a sample examined under the microscope shows unitary orange-red needles. The whole is allowed to cool to C., filtered with suction, and the filter residue is washed with cold dichlorobenpyridine dissolved in 20 parts of ortho'dichlorobenzene, and the whole is heated for 12 hours at -140 C. The 1 mixture is then filtered with suction, and the filter residue is washed with hot ortho-dichlorobcnzene until the washzcne until the washings are colorless. Then the dichlo- 75 ings are colorless, and then washed with methanol until dichlorobenzene and 9 the initially strongly colored washings have become colorless. Theproduct is finally washed with hot water. A By drying the product there is obtained a yellow soft pigment, which imparts to polyvinyl chloride strong red'* dish yellow tints of excellent fastness to migration.

In the following table are given further pigment dyestuffs which are obtained by coupling 2 mols of the aminoaryl-carboxylic acid mentioned in column I with 1 mol of the bis-acetoacetylamino compound mentioned in column II, converting the dyestuif into the dicarboxylic acid dichloride, and condensing the latter with 2 mols of the arylarnine mentioned in column III:

thenadded 4.66 parts of ortho-toluidine and 2 parts of pyridine "dissolved in 40 parts "of ortho-dichloroben'zenc, and the mixture is heated for 12 hours at 135-140 C. The brown coloration of the acid chloride disappears and the mixture acquires a pure yellow color. The whole is then allowed to cool to 90 C., 2 parts of anhydrous sodium acetate are added, and the whole is stirred for a further 5 minutes at that temperature and then filtered with suction. The filter residue is washed with hot dichlorobenzene until the washings are colorless, and it is then washed with methanol and finally with hot water.

I II III IV Tint of material Blaze-component Coupling component Arylamlne dyed with the dyestufl 1-. 4-Ohloro-3-am-ino-benzoic acid--- 4:4-Bis-acctoacetyl-ammo-3:3- Aniline pure orange.

dimethyl-diphenyl. do o-Toluidine orange-yellow.

4-Chloro-2-anisidine reddish yellow.

methane.

dighlorodiphenyl.

phenylene oxide.

thraquinone. do 4 benzene. 4-Amino-diphenyl-4-carboxylic acid. amino-benzene.

o 4:4-Bisacetoacetyl-amino-B:3-

2:6- Bis-acetoacetyl-amino-an- :4-Bis-acetoacetyl-amino-azo- 2: 5-Dichloro-1 :4-bis-acetoaceryl- Chloro-eresidine yellow-orange. Aniline l. Do.

pure-orange. orange-yellow. orange.

greenish yellow.

o-Anisidinc 4-Obloro-2-anisldine-. o-Toluldin'e 'o-Chloraniline o-Anisidine Do. reddish yellow.

.i iiiiiifiilifjiij:ii:i::' .Z:t: iili 5-Ohloro-2 toluidine a dull yellow.

o-Toluidine pureyellow.

do reddish yellow.

do pure yellow.

6-Ohloro-2-toluldine yellow.

Example 4 1n 800 parts of ortho-dichlorobenzene at 100-105 C..

32.8 parts of thionyl chloride are then run in in the course of minutes, and the whole is stirred for 2-3 hours at l05-110 C. The end point of the reaction can be recognized by the cessation of the splitting off of hydrogen chloride, and from the fact thata sample examined under the microscope shows unitary yellowish brown lamellae. The whole is cooled to 80-90 C., then filtered with suction, and the crystals are washed with dichlorobenzene until the washings are colorless. The product is then washed with benzene and petroleum ether, and dried in vacuo at -50 C. There are then obtained about 70 parts of the dicarboxylic acid dichloride of the formula After being dried, the product is a yellow soft pigment, which, when rolled into polyvinyl chloride, yields strong reddish yellow dyeings of very good fastness to migration.

Dyestufis having similar properties are obtained by using in this example, instead of the ortho-toluidine, aniline, ortho-anisidine, S-chloro-Z-aminotoluene or 2:5- climethylaniline.

Example 5 34.5 parts of 2:5-dichloro-l:4-phenylene diamine are stirred in 140 parts of glacial acetic acid, and 34 parts of diketene are run in at 40 C. while stirring well. The temperature of the reaction mixture rises spontaneously to 95 C. When, in a short time, a clear solution is obtained, the dicondensation product begins to crystallise out. The whole is stirred for 1 hour at -95 C. and is then allowed to cool to room temperature. The thick crystalline magma is filtered ofi with suction, washed with It is a yellowish brown crystalline powder, which is only slightly soluble in the usual organic solvents. When heated it decomposes at temperatures above 270 C.

14.96 parts of the acid chloride so obtained are stirred with 0.1 part of thionyl chloride in 200 parts of orthoheated to -105 C. There are acetic acid of 40% strength, and then with cold water until the washings are neutral to litmus. By drying the product there is obtained 2:S-bis-acetoacetylamino-l:4- dichlorobenzene as a white crystalline powder in excellent yield. It dissolves in dilute caustic alkali solutions to give a clear colorless solution. It melts at 205-206 C.

1 l. In the same manner there are obtained the following bis-acetoacetic acid arylides which have not hitherto been described in the literature.

2-ch1oro-1:4-bis-acetoacetylaminobenzene, melting at 2: 6-dichloro-1 4-bis-acetoacetylaminobenzene, melting at 2:3:5z6-tetrachloro 1:4 bis acetoacetylaminobenzene,

melting at 142-143.5 C.

2-rnethyl-1:4-bis-acetoacetylaminobenzene, melting at Z-methyl-S chloro-l :4-bis-acetoacetylaminobenzene, melting at 190192 C.

2:6 dimethyl 3:5-dichloro-1:4bis-acetoacetylamino-- What is claimed is: V 7 1. An azo-dyestutf which is free from groups imparting solubility in water and corresponds to the formula CHI C NHCOC (JO N=N- HC ONE (XL CHI in which B and R represent members selected from the group consisting of benzene and diphenyl radicals, 7R, represents an aryl radical having at most 4 benzene nuclei which are directly connected with one another and X represents a member selected from the group consisting of an acetoacetylamino radical bound by the amide nitrogen atom to R and by the methylene group to'the azo group, and of a pyrazolone-S radical bound by the N! atom in l-position to R and by the methylene group to the azo group, the radicals R R and B bearing as sub stituents members selected from the group consisting of hydrogen and halogen atoms, and lower alkyl, lower alkoxy, nitro and benzoylamino groups.

2. An azo-dyestufi which is free from groups impart ing solubility in water and corresponds to the formula in which R and B represent radicals selected from the group consisting of benzene and diphenyl radicals and R represents an aryl radical having at most 4 benzene nuclei which are directly connected with one another, the radicals R R and B hearing as substituents members selected from the group consisting of hydrogen and halogen atoms, lower alkyl, lower alkoxy, nitro and benzoylamino groups.

3. An azo-dyestuft which is free from groups imparting solubility in water and corresponds to the formula in which B and R represent benzene radicals, and R a benzene radical in which the --NH- groups are in 1,4- position and which contains at least one substituent selected from the group consisting of chlorine atoms, and methoxy and methyl groups.

4. The azo-dyestufi of the formula CH: Cl

NHCOCHN=N (:0 =N- HCONH l CH:

CH: ONH

5. The azo-dyestufi of the formula 6. The azo-dyestufi of the formula 2,936,806 13 14 7. The ezo-dyestufi of the formula ClG-N -N-CO c1 01 (I) GO N=N HG ONE (l: CH1

Ht 1 CH: 0513C 8. The azo-dyestufi of the formula 01 ODOR: 00H:

NH 01 NHCO $0 on on 6 cm cm 5 o o N=N(JHCONH j-NHOOH-N=N References Cited in the file of this patent UNITED STATES PATENTS 2,591,470 Schmid et a1. Apr. 1, 1952 

1. AN AZO-DYESTUFF WHICH IS FREE FROM GROUPS IMPARTING SOLUBILITY IN WATER AND CORRESPOND TO THE FORMULA 